At the heart of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected data tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating, but when the disk rotates air is swirled by the rotating disk, creating an air bearing. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The write head includes at least one coil, a write pole and one or more return poles. When current flows through the coil, a resulting magnetic field causes a magnetic flux to flow through the coil, which results in a magnetic write field emitting from the tip of the write pole. This magnetic field is sufficiently strong that it locally magnetizes a portion of the adjacent magnetic media, thereby recording a bit of data. The write field then, travels through a magnetically soft under-layer of the magnetic medium to return to the return pole of the write head.
A magnetoresistive sensor such as a Giant Magnetoresistive (GMR) sensor or a Tunnel Junction Magnetoresistive (TMR) sensor can be employed to read a magnetic signal from the magnetic media. The magnetoresistive sensor has an electrical resistance that changes in response to an external magnetic field. This change in electrical resistance can be detected by processing circuitry in order to read magnetic data from the magnetic media.
With ever increasing data density requirements it becomes necessary to write ever smaller bits of data onto a magnetic media. This presents challenges in terms of ensuring that the recorded bits are thermally, magnetically stable. Thermal stability of the bits can be achieved by constructing the magnetic media with a higher magnetic coercivity and magnetic anisotropy, however, this also requires a higher write field to record the data, which is difficult to achieve with the necessary smaller write pole. One way to overcome this challenge is through the use of Microwave Assisted Magnetic Recording (MAMR), wherein an oscillating magnetic field is generated near the write pole. This oscillating magnetic field magnetically excites the magnetic media, making it easier to write to. However, in order to be effective, the magnetic oscillator used to generate the oscillating magnetic field must be both thermally robust, having a long life and also efficient so as to generate a sufficiently strong magnetic field.